1. Field of the Invention
The present invention relates to a drive train of a motor vehicle with an internal combustion engine, a transmission and a flywheel mass arrangement assigned to a torque transmission path between the internal combustion engine and the transmission, the flywheel mass arrangement has a drive-side flywheel mass assigned to a driven shaft of the internal combustion engine, a transmission-side flywheel mass assigned to an input shaft of the transmission, and a gear arrangement which is connected between the two flywheel masses which are rotatable at least to a restricted extent relative to one another or between part flywheel masses thereof which are rotatable at least to a restricted extent relative to one another, the gear arrangement is effective in at least one operating state for transmitting at least part of a torque flow between the internal combustion engine and the transmission. The gear arrangement includes at least one planet wheel which is coupled via a meshed engagement with a sun wheel or a ring wheel and is rotatable at least to a restricted extent about a planet wheel axis. The planet wheel has at least one rotational additional mass, the center of gravity of which is offset relative to an axis of rotation assigned to said additional mass, the gear arrangement converting a relative rotation of the two flywheel masses or part flywheel masses into a rotation of the additional mass about the axis of rotation assigned to the latter, with the center of gravity being displaced radially in relation to a flywheel mass axis of rotation.
2. Description of the Related Art
To improve the dynamic behavior of the drive train of motor vehicles, torsional vibration dampers are arranged in the torque transmission path between the internal combustion engine and the transmission and recently are often designed as so-called two-mass flywheels. In the latter case, dividing the flywheel mass into two flywheel masses ensures that resonant frequencies of the gear and of the drive train are well below the frequencies of vibrations emanating from the internal combustion engine (engine). This avoids resonances which may lead to noises, such as gear rattling and body drumming.
In the design of the torsional vibration damper, if appropriate the two-mass flywheel, it is often a conflict of aims as regards the resulting rigidity of the torque transmission path. Thus, a low torsional rigidity, that is to say a low value of the c-value usually described in terms of Nm/degrees would be advantageous for low rotational speeds so that the engine could be started with as little noise as possible. By contrast, a higher torsional rigidity should be ensured at higher rotational speeds so that the maximum torque of the internal combustion engine may be covered.
Conventional torsional vibration dampers usually operate with the same c-value over the entire rotational speed range. As a result, these conventional torsional vibration dampers are too rigid under some circumstances such as at low rotational speeds where the internal combustion engine can still exert a little torque.
A two-mass flywheel is disclosed in German reference DE 42 00 174 A1 in which a primary-side flywheel mass and a secondary-side flywheel mass are coupled via toggle lever arrangement. A mass accumulation which generates between the flywheel masses a centrifugally induced return force which increases with a rotational speed of the two-mass flywheel is provided proximate a pivot bearing between a primary-side lever and a secondary-side lever. The coupling of the flywheel masses via the toggle levers leads to an inertia matrix which defines the dynamic properties of the two-mass flywheel and has matrix elements which are dependent on a relative rotary angle of the flywheel masses. This arrangement also leads to a rigidity which is undefined at zero rotational speed from which nndesirable effects may consequently arise such as, for example, disturbing noises when the engine is started.
Another two-mass flywheel is disclosed in German reference DE 197 26 477 A1 in which a gear arrangement and a torsion damper spring arrangement each have a torque-transmitting effect between a primary flywheel and a secondary flywheel rotatable to a restricted extent relative to the latter. The gear arrangement comprises a plurality of planet wheels in a meshed engagement with a ring wheel fixed in terms of rotation relative to the secondary flywheel mass. Each of the planet wheels are assigned at least one additional mass and arranged so that the center of gravity of the at least one additional mass is displaceable radially in relation to an axis of rotation of the two-mass flywheel as a function of a relative rotary position of the ring wheel and of the planet wheel carrier to change a moment of inertia of the two-mass flywheel. This arrangement of a two-mass flywheel takes effect as a selfsteadying system since there is no definite resonant point.
The reference DE 197 26 477 A1 does not mention centrifugally induced return forces acting on the two flywheel masses. However, an analysis of the system disclosed in FIG. 1 of DE 197 26 477 A1 reveals that a centrifugally induced return force increasing with a rotational speed of the two-mass flywheel occurs at all events and takes effect between the primary flywheel mass having the planet wheel carrier and the secondary flywheel mass connected fixedly in terms of rotation to the ring wheel. Whether this centrifugally dependent return force is at all relevant, as compared with a spring arrangement acting between the two flywheel masses, cannot be inferred from the preliminary publication because of a lack of information on the spring forces in the masses. As far as information regarding the different embodiments disclosed in DE 197 26 477 A1 together with the information on the relative angles of rotation between the two flywheels applies to the arrangement of the additional masses to the planet wheels, the arrangement is such that the return force acts on both sides of an unstable intermediate relative rotary angle position of equilibrium, which lies between two relative rotary angle boundary positions delimiting a relative rotary angle range of the flywheel masses, in the direction of the respective nearer relative rotary angle boundary position. It follows from this that the spring arrangement acting between the flywheel masses is required and, moreover, must have a sufficiently high spring force, since otherwise, at least at high rotational speeds, there is the risk that the two flywheel masses may assume a relative rotary position corresponding to the relative rotary angle boundary positions and torsional vibrations may correspondingly be damped at most only incompletely.
A torque converter with a planetary gear which serves for coupling a turbine wheel and a piston of a bridging clutch is known from European Patent No. 0 306 169 B1.
The object of the present invention is to provide a drive train in which the torque transmission path has lower effective rigidity in a range of lower rotational speeds than in a range of higher rotational speeds so that an internal combustion engine can be started with as little noise as possible and a maximum drive torque capable of being exerted by the internal combustion engine may be conducted by the drive train.
To achieve this object, a drive train of a motor vehicle with an internal combustion engine, a transmission and a flywheel mass arrangement assigned to a torque transmission path between the internal combustion engine and the transmission is provided in which the flywheel mass arrangement has a drive-side flywheel mass assigned to a driven shaft of the internal combustion engine, a transmission-side flywheel mass assigned to an input shaft of the transmission, and a gear arrangement which is connected between the two flywheel masses which are rotatable at least to a restricted extent relative to one another or between part flywheel masses thereof which are rotatable at least to a restricted extent relative to one another, the gear arrangement is effective in at least one operating state for transmitting at least part of a torque flow between the internal combustion engine and the transmission. The gear arrangement includes at least one planet wheel which is coupled via a meshed engagement with a sun wheel or a ring wheel and is rotatable at least to a restricted extent about a planet wheel axis. The planet wheel has at least one rotational additional mass, the center of gravity of which is offset relative to an axis of rotation assigned to said additional mass, the gear arrangement converting a relative rotation of the two flywheel masses or part flywheel masses into a rotation of the additional mass about the axis of rotation assigned to the latter, with the center of gravity being displaced radially in relation to a flywheel mass axis of rotation.
The additional mass is arranged on the planet wheel such that, at least in the operating state, in a relative rotary angle range of the two flywheel masses or part flywheel masses a centrifugally induced return force increasing with a rotational speed of the flywheel mass arrangement and acting on the flywheel masses or part flywheel masses occurs in the direction of a first relative rotary angle position of the two flywheel masses or part flywheel masses which lies between two relative rotary angle boundary positions delimiting the relative rotary angle range.
In addition to the centrifugally dependent return force, an elastic return force exerted by torsion damping springs or the like may also be provided between the flywheel masses or part flywheel masses. If torsion damping springs are provided, then the centrifugally induced return force should be sufficiently high, as compared with the elastic return force exerted by the torsion damping springs to influence the effective rigidity appreciably and to achieve a sufficient increase in rigidity at least at higher rotational speeds. However, since the first relative rotary angle position, which is preferably independent of the rotational speed, lies between the relative rotary angle boundary positions, the torsion spring arrangement or the like acting between the flywheel masses or part flywheel masses may be dispensed with completely, without any losses in the damping of torsional vibrations and even without the fear that the drive-side and the transmission-side flywheel mass will come into rotational abutment along the lines of action as a single flywheel mass system, in the relative rotary angle boundary position.
In one embodiment of the present invention, at least one additional mass may be formed by the mass of a respective planet wheel itself. Alternatively or additionally, at least one additional mass may be formed by the mass of an additional wheel assigned to a respective planet wheel and in meshed engagement with the latter.
There may be arranged in the torque transmission path between the internal combustion engine and the gear a two-mass flywheel which comprises a primary flywheel assigned to the drive-side flywheel mass and a secondary flywheel assigned to the transmission-side flywheel mass. The secondary flywheel may have frictional surfaces of a friction clutch device assigned to the flywheel.
Alternatively, a hydrodynamic clutch device such as a hydraulic clutch or a torque converter may be arranged in the torque transmission path between the internal combustion engine and the gear. The hydrodynamic clutch device comprises a housing and a hydrodynamic circuit formed in the housing. The housing may be arranged to comprise part of the drive-side flywheel mass. Furthermore, a turbine blade arrangement of a turbine wheel of the hydrodynamic circuit may be arranged to comprise part of either the drive-side flywheel mass or the gear-side flywheel mass.
Preferably, the hydrodynamic clutch device has a bridging clutch. If the turbine blade arrangement is part of the drive-side flywheel mass, the turbine blade arrangement is directly couplable via the bridging clutch to the drive-side flywheel mass comprising the housing (when the bridging clutch is in the engaged state). With the bridging clutch disengaged, the turbine blade arrangement is coupled indirectly to the drive-side flywheel mass, specifically via the hydrodynamic circuit.
The turbine blade arrangement assigned to the drive-side flywheel mass may be rotatable at least to a restricted extent relative to a turbine wheel hub which is in torque-transmitting connection to a transmission input shaft and which is assigned to the transmission-side flywheel mass. In this case, it is preferable for torque to be capable of being transmitted via the gear arrangement between the turbine blade arrangement and the turbine wheel hub. For this purpose, the turbine blade arrangement may have a portion serving as a planet wheel carrier or be coupled or couplable fixedly in terms of rotation to a separate planet wheel carrier. If the turbine blade arrangement is coupled or couplable to a separate planet carrier, the piston of the bridging clutch may serve as the separate planet wheel carrier. The piston may function as a planet wheel carrier, despite the axial displaceability of the piston. Therefore, the toothings of the planet wheel and of the ring wheel or sun wheel and/or a bolt portion of the planet wheel carrier (i.e., the piston) for supporting the respective planet wheel, must be designed with the effect of providing axial displaceability, if appropriate.
In the embodiment in which the turbine blade arrangement is part of the gear-side flywheel mass, the entire turbine wheel, including the turbine blade arrangement, may be assigned to the gear-side flywheel mass. Preferably, torque is then capable of being transmitted via the gear arrangement between the housing and the turbine wheel.
Furthermore, for the hydrodynamic clutch device, it is proposed, in general, that a planet wheel carrier mounted rotatably relative to the turbine wheel and/or to the housing be coupled or couplable in a torque-transmitting manner to the housing. The planet wheel carrier may be couplable in a torque-transmitting manner to the housing by means of the bridging clutch already mentioned, in which case, as already mentioned, a piston of the bridging clutch preferably serves as a planet wheel carrier.
Furthermore, when the present invention is arranged in a hydrodynamic clutch device, the turbine wheel hub may comprise a toothing which serves as a sun wheel. The hydrodynamic clutch device may have a torque transmission path in which the hydrodynamic circuit and the gear arrangement are connected in series.
A torsional vibration absorber mass active in at least one operating state may be integrated into the torque transmission path between the internal combustion engine and the transmission, for example, in the two-mass flywheel and/or the (if appropriate hydrodynamic) clutch device. This torsional vibration absorber mass may be coupled or couplable to the drive-side or the gear-side flywheel mass. Where the hydrodynamic clutch device is concerned, the piston of the bridging clutch may serve, in the disengaged state, as a torsional vibration absorber mass which is coupled in a centrifugally dependent manner, i.e., in dependence on rotational speed, via the gear arrangement to the turbine wheel and consequently to the gear-side flywheel mass.
For the sake of completeness, it should also be mentioned that the gear-side flywheel mass may, further, be assigned an effective rotational mass of the transmission and a rotational mass of a transmission input shaft.
It is proposed, in general, that the first relative rotary angle position lie essentially in the middle of the relative rotary angle range defining the relative rotatability of the flywheel masses or part flywheel masses. It may also be expedient, however, for the first relative rotary angle position to be offset relative to a middle of this relative rotary angle range, preferably in the direction of an overrun direction of rotation of the flywheel mass arrangement.
As already indicated, a spring arrangement may be operatively arranged between the flywheel masses or part flywheel masses and/or gear components of the gear arrangement and participating in the transmission of the torque flow. When the spring arrangement is referred to in the specification, it is intended to embrace not only arrangements consisting of helical compression springs or the like, but also arrangements formed by any desired elastic elements, for example elastomeric elements. Regarding the embodiment arranged in the hydrodynamic clutch device, it is preferred that the spring arrangement be arranged in an inner torus of the clutch device, wherein the inner torus is delimited by the turbine blade arrangement, a pump blade arrangement of a pump wheel and, if appropriate (in the case of a torque converter), a stator blade arrangement of a stator wheel of the hydrodynamic circuit.
The spring arrangement may also be arranged to take effect between gear components of the gear arrangement. For example, the spring arrangement may be arranged to take effect between at least one planet wheel and the planet wheel carrier.
If a spring arrangement is provided, it is preferred that the spring arrangement is connected in parallel to the gear arrangement and transmits part of the torque flow between the internal combustion engine and the transmission (parallel to that part of this torque flow which is transmitted by the gear arrangement). However, it is also possible for the spring arrangement to take effect between gear components of the gear arrangement such that the spring arrangement only contributes to torque transmission by the gear arrangement (and the torque flow is, under some circumstances, transmitted essentially completely via the gear arrangement). For example, the spring arrangement could take effect between at least one planet wheel and a planet wheel carrier and prestress the planet wheel toward a predetermined rotary position of the planet wheel in relation to the planet wheel carrier. Then, in addition to the centrifugally induced forces which act on the planet wheel as a result of the offset between the center of gravity of the additional mass and the axis of rotation of the additional mass, the planet wheel is also acted on by elastic return forces in the direction of said rotary position or in the direction of another rotary position.
The spring arrangement may be arranged for generating an elastic return force which acts on the flywheel mass or part flywheel mass toward a second relative rotary angle position of the two flywheel masses or part flywheel masses which lies between the two relative rotary angle boundary positions and, if appropriate, is offset relative to the first relative rotary angle position. Preferably, the spring arrangement is prestressed in the overrun direction of rotation of the flywheel mass arrangement by the centrifugally dependent return forces; the first relative rotary angle position is therefore preferably offset relative to the second relative rotary angle position in the overrun direction of rotation.
For many arrangements, it would seem that a spring arrangement, as described above, is highly expedient. As already discussed, however, it is also possible to dispense with such a spring arrangement completely and accordingly obtain an effective rigidity of the torque transmission path which is determined by the rotational speed taking effect. For example, gear arrangement may provide an extremely low rigidity at low rotational speeds and a high rigidity sufficient for transmitting the maximum torque of the internal combustion engine at higher rotational speeds. For this purpose, the two flywheel masses or part flywheel masses may be coupled solely via a coupling device which comprises the gear arrangement and which exerts no appreciable elastic return forces on the flywheel masses or part flywheel masses in the direction of a predetermined relative rotary angle position. In this case, the torque flow may be transmitted essentially completely via the gear arrangement.
Another embodiment of the drive train including the two-mass flywheel or the hydrodynamic clutch device, is distinguished in that the gear arrangement has a gear transmission ratio changing with a relative rotary angle of the flywheel masses or part flywheel masses and influencing the radial displacement of the center of gravity and consequently the centrifugally dependent return force. For this purpose, a toothing may be formed between the planet wheel and a sun wheel and/or the ring wheel with a tooth spacing changing continuously along a respective circumference.
The invention relates, furthermore, to a two-mass flywheel for arrangment in a motor vehicle drive train between an internal combustion engine and a transmission, comprising a primary flywheel assigned to a driven shaft of the internal combustion engine, a secondary flywheel assigned to an input shaft of the transmission, and a gear arrangement which, in at least one operating state, takes effect between the two flywheels rotatable relative to one another at least to a restricted extent and which, in this operating state, transmits at least part of a torque flow between the internal combustion engine and the transmission. The gear arrangement comprises at least one planet wheel which is coupled to a sun wheel and/or a ring wheel (in particular, in a meshed engagement with the sun wheel and/or the ring wheel) and is rotatable at least to a restricted extent about a planet wheel axis. The planet wheel has at least one rotatable additional mass with a center of gravity offset relative to an axis of rotation assigned to said additional mass. The gear arrangement converts a relative rotation of the two flywheels into a rotation of the additional mass about the axis of rotation assigned to the latter, with the center of gravity being displaced radially in relation to a flywheel axis of rotation.
According to the invention, there is provision for assigning the additional mass to the planet wheel such that a centrifugally induced return force increasing with a rotational speed of the two-mass flywheel and acting on the flywheels occurs in the direction of a first relative rotary angle position of the two flywheels which lies between two relative rotary angle boundary positions delimiting the relative rotary angle range of the two flywheels.
The two-mass flywheel according to the invention, which is provided preferably for a drive train, may be designed according to the above description of the torque transmission path, in particular the gear arrangement and the two-mass flywheel, of the drive train according to the invention. In this case, the primary flywheel may be identified as a part flywheel mass of the drive-side flywheel mass and the secondary flywheel may be identified as a part flywheel mass of the transmission-side flywheel mass.
The invention further relates to a hydrodynamic clutch device such as a hydraulic clutch or a torque converter for arrangement in a motor vehicle drive train between an internal combustion engine and a transmission. The hydrodynamic clutch comprises a housing, a hydrodynamic circuit formed in the housing and having a turbine wheel mounted rotatably in the housing. The hydrodynamic clutch further comprises a gear arrangement which, in at least one operating state of the clutch device, has a torque-transmitting effect in a torque flow path between an input side and an output side of the clutch device. The gear arrangement comprises at least two gear elements moveable relative to one another.
According to the invention, there is provision for the gear arrangement to be assigned at least one additional mass, the center of gravity of which is displaceable radially in relation to an axis of rotation of the clutch device as a function of a relative position of the gear elements. The displacement of the at least one additional mass changes a moment of inertia of the clutch device and/or generates, at least in the operating state, a centrifugally dependent return force which acts between two rotary parts rotatable at least to a restricted extent relative to one another and located in the torque flow path between the input side and the output side, in the direction of the first relative rotary angle position.
Preferably, the first relative rotary angle position lies between two relative rotary angle boundary positions delimiting a relative rotary angle range of the rotary parts. The hydrodynamic clutch device according to the invention, which is provided preferably for a drive train may, furthermore, be designed according to the above description of the torque transmission path, in particular the gear arrangement or the hydrodynamic clutch device, of the drive train according to the invention. In this case, the housing of the clutch device may be identified as a part flywheel mass of the drive-side flywheel mass. According one embodiment, the entire turbine wheel may be identified as a part flywheel mass of the transmission-side flywheel mass. According to another embodiment, the turbine blade arrangement of the turbine wheel and the housing may be identified as a part flywheel mass of the drive-side flywheel mass, while a hub of the turbine wheel may be identified as a part flywheel mass of the transmission-side flywheel mass.
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein.